JOURNAL OF COMPOSITE MATERIALS Article Zinc oxide nanorod as effective reinforcing material for enhancing b phase crystal in poly(vinylidene fluoride) filaments Prasanta K Panda , Sachin R Tambe and Amol G Thite Abstract The present work is an attempt to demonstrate that incorporation of small amount of zinc oxide nanorods enhances the  crystal percentage, which is essential for improvement in piezo-electric performance of the poly(vinylidene fluoride) (PVDF) fiber. The zinc oxide nanorods were synthesized with aspect ratio of 26 and uniformly dispersed in PVDF by melt compounding process. Those compounded polymers were melt spun and subsequently cold drawn to obtain composite filaments. The effect of nanostructure, loading amount, melt draw ratio, cold draw ratio, and drawing temperature was investigated. The incorporation of nanorods resulted in 14% increase in  phase crystal content compared to control PVDF filaments. The  phase crystal content has been analyzed using the wide-angle X ray diffraction and FTIR spec- troscopy. This increase in  phase crystal content was 10% more compared to circular zinc oxide nanoparticle reinforced PVDF composite filament. There was no significant change in mechanical properties of the composite filaments com- pared to the control PVDF filament. Keywords Polyvinylidene fluoride, zinc oxide nanorods, melt spinning, composite filament,  crystal Introduction Polymeric smart material is a fast-growing research area to develop smart materials with enhanced effi- ciency. Among the smart materials, piezoelectric mater- ials are widely used due to their fast-electromechanical response. Ceramics are well accepted piezoelectric material. However, in certain applications, polymeric piezoelectric materials are suitable over the ceramic due to their unique properties such as higher piezoelec- tric stress constant, processing flexibility, toughness, high strength, and high impact resistance. Piezoelectric property in poly(vinylidene fluoride) (PVDF) was first observed in 1969. Thin PVDF films that had been poled exhibited a very large piezoelectric coefficient, 6–7 pCN 1 , a value, which is about 10 times larger than had been observed in any other polymer such as PAN and PVC. From the structural point of view, PVDF is a semicrystalline and polymorphic material and shows at least four crystal phases at dif- ferent processing condition. Among the four crystal phases, the polar  phase crystal shows piezo, pyro, and ferroelectric characteristic due to the all trans-conformation in orthorhombic unit cell. Thus, the amount of  phase crystal should be as high as possible to enhance the piezoelectric property of PVDF. The most stable  phase of this polymer forms during melt crystallization. This stable  phase can be transformed to  phase by application of mech- anical force below the temperature 100  C. The polar- isation process further helps to improve the piezoelectric property by increasing uniformity in align- ment of dipole moments in the unit cell of  phase. 1 Other than the mechanical stretching, the enhancement in  phase content is also possible by incorporation of nanoparticles in the polymer due to large surface area of interaction. 2 Incorporation of various nanofillers such as amino modified double wall carbon nanotube, 3 carbon black, 4 SiO 2 nanoparticle, 5 and multiwalled The Bombay Textile Research Association, India Corresponding author: Prasanta K Panda, The Bombay Textile Research Association, LBS Marg, Mumbai 400086, India. Email: nanolab@btraindia.com Journal of Composite Materials 0(0) 1–7 ! The Author(s) 2020 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/0021998320921548 journals.sagepub.com/home/jcm